CBSE Electrical Machines Theory Question Paper Class 12th (2010)

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Series OSS                                                                                                                        Code No. 103

                                                                                 ELECTRICAL MACHINES
                                                                                     (Theory) Paper II

Time allowed : 3 hours                                                                                          Maximum Marks : 40

Instructions : Attempt all questions.


1. Draw a neat circuit diagram of a compound motor and give its applications. Explain how a compound motor combines the advantages of both shunt and series type of d.c. motors.    4+2+4
Explain why a starter is required for starting a d.c. shunt motor. Draw the connection diagram of a starter in conjunction with a d.c. shunt motor complete with protective devices. Write the function of protective devices.    4+4+2


2. (a) What is a diode ? What are its applications in half wave and full wave rectifiers ? Explain with diagrams.    1+2+2
    (b) What is transistor ? What is its use in a voltage stabilizer ?    3


3. (a) Explain the difference between ordinary transformer and auto transformer.    4
    (b) A 55 kVA, 11000 V/220 V, 50 Hz single-phase transformer has 50 turns on the secondary side. Determine    2+2+2
(i)      number of turns on primary side
(ii)     value of primary and secondary current at full load
(iii)    transformation ratio


4. Describe the construction and principle of operation of a 1-pliase capacitor run Induction motor with neat sketches.
What are various faults which are likely to occur in a 1-phase Induction motor ? Write their remedies.

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